As known in the art, notch antenna elements (or more simply “notches”) are frequently used in the design of linear and planar array antennas. Such arrays may operate with multiple polarizations. The spacing between notches is referred to as the lattice constant of the array, and is constrained by electromagnetic principles to be no greater than a certain value in order to prevent unwanted array characteristics known as Bragg or grating lobes. On the other hand, minimum spacing is constrained by the ability to package and integrate the electronics to provide signals to and from the array, as well as the economics of total antenna element and active channel count which increases with decreasing spacing between elements in the array.
Attempts to properly size array antennas using notch radiators in confined spaces, such as airborne pods, missile bodies, wing leading edges, etc. is therefore a balance between ideally maximizing the total array area while fitting within available volume. If it is necessary to package electronics more densely than desired for the array, a “dilation” layer is typically employed which mechanically translates the necessary connections from the electronics spacing to the notch element spacing. This dilation adds depth to the overall system and adds signal loss in the system.
Correspondingly, in the opposite direction, if electronics cannot be packaged down to the scale needed for the desired array spacing that prevents grating lobes, a dilation layer with a negative scale factor permits connection of the necessary feeds from the larger electronics spacing to the smaller array element spacing. This too adds depth to the overall installation and incurs power losses.